سنن ابن ماجه

It was narrated from 'Umar, meaning, from his father, his grandfather 'Umar, that : he gave a horse in charity at the time of the Messenger of Allah (ﷺ), then he saw its owner selling it for a low price. He went to the Prophet (ﷺ) and asked him about that, and he said: “Do not buy what you gave in charity.”